*Maximum processor frequency is 5 MHz. IBM PC used one 14.31818 oscillator to drive both the CPU and video. For video it was divided it by 4 (14.31818 / 4 = 3.58 MHz), and for CPU it was divided by 3, which why it was running at 4.77 MHz, and not at 5 MHz.

**Initially, there was no IBM support for hard drives at all. The limits were:

- DOS 1.0 and 1.1 had no hard drive support.
- The BIOS on the 5150 motherboard has no support for hard drives.
- 'BIOS expansion ROM' functionality did not exist at this time.
- The IBM 5150's 63W power supply was inadequate to power both the 5150 and hard drives of the time.

However, some third-party solutions emerged. They involved an externally powered hard drive, and custom boot floppy.